I have a 4 year old, vinyl lined, 35,000 gallon "lazy ell" in ground pool with Grecian Ends. I have been using a Dolphin Dynamic Pro with Remote several times per week since the middle of July. I loved it.

However, two weeks ago I started getting overnight water loss of 5 inches. After refilling and dropping for three days, I turned off the pump and allowed the leak to free fall to try and determine the source.

In addition, my plumber and I pressure tested all of the plumbing, including the main drain. As the water passed the lights and headed for the bottom of the steps, I turned the water back on to maintain water pressure on the liner.

The Guy that does the leak detection service returned from the Bahamas and came out last Wednesday. What we found, by diving, were 150+ slits, the size of a dime to a quarter, around the shallow end only, where the floor meets the wall!
My guy made patches from the vinyl leftover from cutting out the stairs and the swimout. He had me all patched up in less than two hours. Some of the slits were covered by on long patch. I am 4 days with zero loss.

We believe the culprits are the nylon wheels on the outside of the tractors. I had the Dolphin set for wall climbing/waterline cleaning, and I had noticed that it almost never made it up the shallow end walls, because it is a 90 degree angle. Also the Grecian ends give it an irregular pattern to learn. But it would keep banging into the walls during its cycle, to try and climb. The liner at the bottom of the wall is snug, but if you press your finger in it does spring back like there is some space behind it.

I am actually going to run the Dolphin on the Floor Only mode and see if it will behave. Because it does clean amazingly.

On a brighter note, I did use the down time to replace my Hayward 2HP Super Pump with a Pentair Whisperflow 2 Speed Pump. I will post a review after I get my next electric bill. But the 1/2 hp setting is so quiet it Purrs. {and draws 3.5 amps instead of 10.5}